1. Field of the Invention
The invention relates to an image forming apparatus for forming an image by an electrophotographic system.
2. Related Background Art
In such a kind of apparatus, there is a case where when a power supply is turned on, a specific command (ID) is transmitted from a printer controller to a printer engine and the printer engine can operate only when the contents of the command coincide with a predetermined code.
FIG. 6 shows a block diagram for explaining a printer control mechanism of an example of a multicolor image forming apparatus. In FIG. 6, reference numeral 1 denotes a printer controller circuit for forming a video signal (VDo) 3 in an image forming apparatus 2 on the basis of a multicolor image signal from a printer controller 11 and outputting it to a laser driver 4. The laser driver 4 is a circuit for driving a semiconductor laser (not shown) and for generating a laser drive signal 5. An actuator driver 54 outputs an actuator drive signal 55 for a motor, a clutch, a solenoid, and the like, in accordance with a print sequence signal 52 from the image forming apparatus 2 or sensor information.
The image forming apparatus 2 outputs first and second video signals formed from the multicolor image signal, forms first and second electrostatic latent images onto an image holding body (not shown), and outputs a drive signal 6 to a bias controller 7. The bias controller 7 outputs a bias signal 8 to a high voltage unit for transfer/development, and the like, of data according to the drive signal, develops the electrostatic latent image, and transfers the developed image onto a recording paper, thereby forming a multicolor image.
In a print sequence controller 83, a print sequence procedure for performing a process in association with the detection of open/close information of a door (not shown) in the image forming apparatus 2 and the normal printing operation is transferred to the image forming apparatus 2. Information of an engine at the time of image formation is reported as a status to the printer controller 11 from an informing unit 81 through a video interface 18.
The operation between the printer controller circuit 1 and printer controller 11 will now be described with reference to FIG. 7 and FIGS. 8A and 8B. FIG. 7 shows an example of timing charts for interface signal lines for connecting the printer controller circuit 1 and printer controller 11. FIGS. 8A and 8B show examples of timing charts for command timings and status timings, respectively.
In FIG. 7, after the power supply is turned on, the printer controller circuit 1 makes a /PPRDY signal 21 true at a time point when communication with the printer controller 11 is enabled. After it is confirmed that a /CPRDY signal 23 from the printer controller 11 is true, when it is recognized that a proper ID code is received from the printer controller 11, the image forming apparatus 2 starts a process for setting a printable state. When the apparatus enters the printable state, a /RDY signal 22 is made true.
At a time point when the communication is possible, as shown in FIG. 8B, the printer controller 11 makes the /CPRDY signal 23 true and makes a /CBSY signal 24 true. After that, the printer controller transmits a CMD signal 25 synchronously with a pulse from a CCLK signal 26. After a command from the CMD signal 25 is transmitted, a CBSY signal 24 is made false.
When the command is received by the above procedure, the printer controller circuit 1 makes an SBSY signal 27 true and, after that, transmits an STS signal 28 synchronously with the pulse from the CCLK signal 26. After the status by the STS signal 28 is sent, the SBSY signal 27 is made false. By the above procedure, the printer controller circuit 1 and printer controller 11 executes transmission and reception of the command and status.
A procedure for the printing operation will now be described.
The printer controller 11 makes a /PRNT signal 29 true after confirming that the /RDY signal 22 is true.
When it is confirmed that the /PRNT signal 29 is trues as shown in FIG. 8A, the printer controller circuit 1 starts the pre-rotating operation of an electrophotographing process. After a reference signal (not shown) is detected, the printer controller circuit 1 generates a pulse of a TOP signal 30 after the elapse of time t1. The printer controller 11 generates a yellow image signal /VDo 32 synchronously with a pulse of an LSYNC signal 33. By similar means, image signals of magenta, cyan, and black are outputted, thereby forming a multicolor image.
FIG. 9 is a flowchart showing the printing operation sequence in the printer engine of the image forming apparatus, and will be sequentially described hereinbelow in accordance with the processing steps in the diagram.
When the power supply is turned on, an initial setting of a hardware circuit and communication is performed. After that, the apparatus enters a state of waiting for a proper ID command from the printer controller (step S10). When it is determined that the proper ID command is received, the processing routine advances to step S11 and initial processes, for example, leading processes such as checking for the presence or absence of a developer, starting of adjustment of a temperature of a fixing heater, initialization of a driving system, and the like, are executed until a standby state in which the printing operation is enabled. At this time, however, when a failure is detected by the self diagnosis, the processing routine advances to a failure routine.
The apparatus waits for the standby state, which is a state in which a fixing temperature reaches a target temperature or the like (step S12), thus enabling the apparatus to "stand by" to be ready to execute a printing operation, as discussed above. When the apparatus enters the standby state, paper presence/absence information from paper presence/absence detecting means (not shown) is checked (step S13). If paper is present, step S14 follows. If no paper exists, step S12 follows.
In step S14, the presence or absence of a print instruction from the printer controller is discriminated (a check is made to see if the /PRNT signal is true). If there is a print instruction, a print sequence of the electrophotographing process is executed (step S15) and an optimum image is outputted. When the printing operation is finished (step S16), a process to return to the standby state is executed and the operations from step S12 are repeated.
When the power supply is turned on, unless the reception of the proper ID command is confirmed, the printer engine does not execute the operation (prevention of abuse by forgery printer controller).
When an error occurs in the print image, it is necessary for the service person, and the like, to remove the printer controller, to perform the printing operation, and to discriminate whether the error occurred due to the engine or the controller. In the printer engine, as mentioned above, for this purpose, a special tool to skip the step of discriminating the reception of the ID command is attached to the printer engine, thereby enabling execution of an engine test print.
However, the service person executes services and adjustments of a plurality of business machines and, when he does not have the above special tool, he cannot make the printer engine operative and has to again visit the user. This deteriorates the service adjusting performance of the service person and increases costs.